In many RF electronic circuit configurations, there is a need to supercool the electronic circuits for improved performance. For example, a thermally cooled amplifier has a lower noise figure than an amplifier operated at ambient temperature. Emerging cryogenic microwave receiver systems that provide enhanced speed and sensitivity include cryogenic cooled components such as cooled mixers and superconductive components for handling signals. These systems place difficult demands on signal connections. The connections to these systems include one end typically at ambient temperature, and an opposite end at a cryogenic temperature. It is highly advantageous to reduce heat conduction along the RF coaxial signal connections to maintain the receiver components at the cryogenic temperature without placing excessive demands on the receiver system refrigeration unit, which commonly has limited cooling capabilities. Input and output via the connections is difficult because the connections need to present minimal thermal load while simultaneously minimizing transmission loss to the input and output signals. The efficiency and power dissipation in the refrigeration units is determined by the refrigeration power supply. The lower the heat load imposed by RF connections, the lower the temperature the refrigeration unit can cool the amplifier, producing a lower overall amplifier noise figure. Consequently, it is important to reduce the heat leakage along RF connections to the cryogenic system.
The problem of providing an input/output RF connection is fundamentally challenging because all materials having high electrical conductivity also have high thermal conductivity. No existing coaxial RF connection solves this problem.
In addition, connections for such cryogenic systems should have low insertion loss, which is a measure of transmission efficiency. Low insertion loss relates to reduced power loss during transmission.
Thus, there is a need for an improved RF connection that has (i) very low thermal conductivity, and (ii) low insertion loss over a range of frequencies.